I just got my daughter a HTC Tilt. It has windows mobile 6, windows media player, office, wifi, a gps receiver, 3.0mp camera and uses micro sd cards. With an 8gb card it has as much memory as her ipod does. The touchscreen works great but it has afull keyboard too so it gives you an option. I may swap my blackberry for one myself.
I have the Samsung Epix and enjoyed it so far. I find myself using the optical mouse a majority of the time and keyboard is easy to type email and text messages.
I have the Sprint Mogul which is a slightly older version of the AT&T Tilt. It is slightly bulky and the buttons on the touch screen make it almost mandatory to use the stylus for anything.
With that said, all of my business and personal emails sync to it at whatever interval I want them to and the productivity can't be beat. It has built in gps that is sub-meter accurate.
Additionally, there are unlimited apps and hacks that you can add to it to make it do just about anything you might ever need.
My favorite add-on so far is app that makes the phone into a wireless access point so that you or whoever else can use (tethering) the 3G network from the phone wirelessly.
After 2 weeks my daughter is still loving her tilt and I am sold on getting one when I can get a discounted one in February. Think I can last a couple of months without to save a few hundred. The built in stylus is great since I hate fingerprints on a screen.